Five questions with Kei Nishikori

He was 18 years old when he blew through the field six years ago at Delray Beach for his first ATP World Tour title.

Kei Nishikori, playing less than 200 miles from his primary school -- Nick Bollettieri's Tennis Academy -- won three qualifying matches and ripped off five main-draw victories in a row, beating Sam Querrey in the semifinals and James Blake in the final. Nishikori dropped the first set in both of those matches, but found a way to prevail.

He entered the tournament ranked No. 244 and emerged at No. 131 with $68,800 in his pocket -- and, suddenly, a name in the game. It was a dramatic return on the investment of former Sony CEO Masaaki Morita, who funded a three-year tenure at Bolletieri's. Nishikori did some other nice things in 2008, winning a Challenger in Bermuda, taking a set off Rafael Nadal in the third round of Queen's and advancing to the fourth round of the US Open.

And yet, for the better part of the next four years, Nishikori never quite seemed to capture the promise of that dazzling breakthrough in Florida. The biggest setback was right elbow surgery that took him out for an entire year. A year ago, he won his second title, at Memphis. In retrospect, maybe those four years were a necessary part of the seasoning process, a college on the court, if you will.

"I gained a lot of experience in that time between titles," Nishikori said Monday evening from his Memphis hotel. "The injury -- I learned a lot of things from that. I'm more patient than I was a few years ago. I don't give as many unforced errors. My serve is much better."

Since the injury, Nishikori has gradually improved his ranking and, at the age of 24, today finds himself at No. 16. Last June, he found himself at a career-best No. 11. That's the highest ATP ranking ever for a Japanese player.

He's a top seed this week, for the first time, at the U.S. National Indoor Tennis Championships in Memphis. In six weeks, he's already off to a terrific start for 2014.

Earlier Monday, Nishikori visited the St. Jude Children's Research Hospital, along with fellow pros Mikhail Kukushkin, Teymuraz Gabashvili and David O'Hare. It was the second visit for Nishikori, who called it an "eye-opening" experience.

ESPN.com queried Nishikori after practice and a stretching session:

ESPN.com: What did you take from the fourth-round Australian Open match with Rafael Nadal, which really came down to just a few points, even though it was straight sets loss -- 6-7 (3), 5-7, 6-7 (3)?

Kei Nishikori: That was the best match I had against Rafa in four or five tries. I had more chances to win a set and I thought I played great. But I'm still a long way from winning against him. I had him 5-4 on my serve in the third with chances, but I was rushing and getting tight. In those moments, the tough guys never give away points. Yeah, I have to be ready for those chances.

ESPN.com: How did it feel to win three points last week in that Davis Cup victory over Canada that got you into a quarterfinal berth opposite the Czech Republic?

Nishikori: It was a great experience, our first time in the second round. My doubles partner [Yasutaka Uchiyama] was great. I take a lot of confidence from that. The Czechs are going to be tough, but we have the advantage of playing at home. I'm going to have to win my singles matches if we want to win, but we are getting better as a team. Hopefully, we can go further.

ESPN.com: What has Michael Chang, working with Dante Bottini, brought to the table as your new coach?

Nishikori: He's here in Memphis with me now. He's giving me a lot of good tips. Little things, like all the little steps I need to make, the techniques I need to take on the court. Mentally, he makes me strong. And also he knows the other players. We just started, but it's a good matchup.

ESPN.com: What do you need to do to break into the top 10?

Nishikori: Yeah, I still think it might take some time to get top 10. I need to do well at all the tournaments, especially the big ones, the Grand Slams. I need to get to at least the quarterfinals or the semifinals of those tournaments. I've been beating top-10 players by being aggressive, stepping into the court. I just need to have fewer unforced errors, for sure. On the important points I need to raise my level.

ESPN.com: One of the perks of being the defending champion in Memphis is the reserved parking place at the Memphis Racquet Club. Have you used it yet?

Nishikori: [Laughing] Yeah. I parked my [Kia] there today. Officially, I'm the defending champion, so that makes me feel good. Hopefully, I can win it again. Maybe the shorter walk to the locker room will help.